Movie 43: why did so many Hollywood stars sign up for the humiliation?

Every director dreams of being compared to Orson Welles. But having your new film labelled "the Citizen Kane of awful" might not be quite what Peter Farrelly had in mind. Movie 43, which opened worldwide last Friday, wasn't actually screened for critics before release. Yet a handful braved the multiplex and paid anyway. Unbuttered by PR largesse, few resisted the chance to unleash both barrels.

"There's awful and THEN there's Movie 43," wrote Richard Roeper in the Chicago Sun-Times. For Peter Howell of the Toronto Star, it is the "worst film ever", and "biggest waste of talent in cinema history". David Edelstein offered cheery counterpoint to the chorus. "It's rare to see a piece of shit that actually looks and sounds like a piece of shit," he wrote in New York magazine. "It's kind of exciting!"

Such a pitch of criticism is proportionate to the expectations one might entertain for a film made by the man behind There's Something About Mary and fronted by a cast which includes two of this year's Oscar nominees – Hugh Jackman and Naomi Watts – as well as the master of ceremonies (Seth MacFarlane). Other big hitters beaming from the poster include Kate Winslet, Uma Thurman, Terrence Howard, Richard Gere, Emma Stone, Liev Schreiber, Gerard Butler, Anna Faris, Johnny Knoxville, Chloë Moretz, Seann William Scott and Jason Sudeikis.

Movie 43 unfolds as a series of skits strung together as pitches presented by a desperate screenwriter (Dennis Quaid) to a producer (Greg Kinnear). Winslet plays a woman dismayed when her date (Jackman) reveals a pair of genitals swinging from his chin. Real-life couple Faris and Chris Pratt share a sex scene in which he defecates on her face. Stephen Merchant and Halle Berry's intimate supper involves breasts plunging into guacamole. Moretz's character has her first period, which alarms her companions so much they call 911. Then a cartoon cat urinates on Elizabeth Banks.

That the bottom has fallen out of the grossout genre is not news; what might have felt edgy in small doses in 1998 inevitably seems stale now. Likewise, ensemble comedies (remember Valentine's Day? Rat Race?) offer a notoriously dodgy template. So it's no surprise Movie 43 is no masterpiece. What has stunned critics, however, is the depth reached, and the star wattage of those plumbing it. Asks Edelstein: "Was someone holding Kate Winslet's children hostage? Threatening to release compromising pictures of Emma Stone? Did Richard Gere or Hugh Jackman have gambling debts?"

Yet in theory you can see the logic in signing up. Many big names enjoy their biggest pay days from back-end contracts, which involve them taking a percentage of the film's profits in return for equity rates up front, and a small initial commitment (in this case, a couple of days, for about $800). If the film flies, they clean up. If it doesn't, it'll probably be buried anyway.

It also gives A-listers the chance to show they've still got their finger on the pulse. Catching the eye of a generation more accustomed to short-form online comedy was, Farrelly has said, one of the film's aims. "With [online comedy site] Funny or Die, there are certain limits. And we just wanted to do that kind of short and go much further." (Although as box office expert Jeff Bock has said, expecting the target market to pay for such content when it's available free online is optimistic.)

Plus, of course, metaphorically or literally strapping balls to your face helps cultivate the impression of a good sport. Industry analyst Charles Gant compares signing up to Movie 43 to showing up in person to collect a Golden Raspberry. "You don't want to get too snooty. The equivalent would be Judi Dench, who has done a bag-lady cameo for the upcoming Run for Your Wife film, which otherwise stars non-Oscar-winning Danny Dyer, Denise Van Outen and Neil Morrissey."

The casting process for a film such as Movie 43 uses a domino effect, with stars signing on once peers have done so. Here, Winslet and Jackman were apparently first on board, shooting their scene more than four years ago. This footage was used as a calling card by producer Charlie Wessler to bag the rest. "The truth is," he told Hollywood Reporter, "I had a lot of friends who were in this movie. And if they didn't say yes, this movie wouldn't have got made."

It does seem that many of the stars tried to jump ship. Farrelly's strategy was aggressive accommodation. "Wait them out. Shoot when they want to shoot. Guilt them to death." While the canny – Colin Farrell, South Park's Trey Parker and Matt Stone – managed to wriggle out, and others resisted altogether ("Fuck off" was reportedly George Clooney's response), some could not escape. Production was moved 3,000 miles to convenience a sceptical Gere.

Strange as it may seem, the inadvertent – or even fraudulent – bagging of a big name is not so unusual. In 2001 Keanu Reeves claimed he was press-ganged into starring in serial-killer thriller The Watcher after a friend forged his signature on the contract. Unable to prove it, he agreed to take the role rather than face a long legal battle. Bill Murray famously signed up to voice slothful puss Garfield under the mistaken impression it had been scripted by a Coen brother.

None of its stars have helped plug Movie 43, but as one insider said, it's unlikely any would have agreed to promotional duties. "When you make an ensemble movie like this, none of the cast agree to support it, as they all hate doing PR, and if they only have small roles, there's no obligation to do it."

Of those we contacted, only Stephen Merchant was willing to share the trauma of making Movie 43: "I had to spend two days looking at Halle Berry. It was a living hell."

The only person who has consistently defended the film is Farrelly, who earlier this week fired back at his critics on Twitter, saying: "Movie 43 is not the end of the world. It's just a $6m movie where we tried to do something different. Now back off … "

The strategy is smart. By focusing attention on its small budget, he can highlight the ease with which it will make money. Such comedies aren't just critic-proof; their prospects are actively boosted by mainstream condemnation. Already in the US, the film has taken $4.8m – not the jackpot, but not peanuts. In Russia, the figure is $8.5m.

And yesterday, figures for the UK came through to reveal a weekend total of £787,648, and a screen average of £2,875. Zero Dark Thirty's, for the record, is £2,426.